The present invention relates, in general, to analog amplifiers and, more particularly, to Radio Frequency (RF) analog buffers.
Receiver circuits are used in a myriad of wireless communication applications such as cordless telephones, pagers, and cellular telephones. A receiver circuit typically receives a Radio Frequency (RF) modulated signal from an antenna. The receiver includes an input low-noise amplifier followed by a filter and a mixer. The RF signals are transmitted at a high frequency and are received by the mixer. The mixer uses a local oscillator signal for downconverting the RF signal to an IF signal for additional processing. It is desirable to maintain the receiver sensitivity, linearity, and noise figure over a wide range of input signal levels and input frequencies.
The RF buffer can be used to provide amplification of the local oscillator signal that is used by the mixer for downconverting the RF signal. Another application for the RF buffer includes buffering a signal for transmission by the transmitter section. The RF buffer is the interface block that provides amplification of the signal generated by the voltage controlled oscillator before being passed to the scaler in a phase lock loop circuit.
RF buffers have been implemented using external transistors, inductors, and capacitors, but the external components take up board space and provide a higher cost solution. The tolerance of the external components used in the manufacture of the prior art RF buffers cause performance problems and fluctuations from one part to another.
Hence, a need exists for an RF buffer that has a wide band of frequency operation, and maintains a constant power level when the power level of the input signal is changing. It would be of further advantage for the RF buffer to be fully integrated and have reduced costs.